It’s pretty simple. They either need federal legislation to say it’s ok for them to be doing this, or it needs to stop being a federal crime, otherwise they are legally required to do exactly what they are doing.
By your right about it being government control stuff, psychological resistance to letting go of the War on Drugs is pretty high, and unless it changes it’s going to remain in the current status quo until enough of them get too old to hold their seats in the House/Senate and new people with less fossilised opinions get to vote on legislation regarding the topic.